local mmi, mma = math.min, math.max

local n, _k = io.read("*n", "*n")
local t = {}
local a = {}
for i = 1, n do
  local ai, m = io.read("*n", "*n")
  a[i] = ai
  local ret = 0
  for j = 1, m do
    local b = io.read("*n")
    ret = mma(ret, t[b] + ai - a[b])
  end
  if 1 < i then ret = mma(ret, t[i - 1]) end
  t[i] = ret
end
local ans = 0
for i = 1, n do ans = mma(ans, t[i]) end
print(ans)